1. Field of the Invention
The present invention relates to a metallic gasket of aluminum materials, which is used disposed between confronting surfaces of engine components, for example cylinder heads, cylinder blocks and others.
2. Description of the Prior Art
Conventionally, a head gasket installed between a cylinder head and a cylinder block is chiefly a metallic gasket composed of thin stainless steel sheets overlaid one on the other. Of various metals, stainless steel is considerably low in heat conductivity. In addition, the metallic gaskets are usually applied with a coating of non-metallic substances, which may result in insufficient heat conduction between the cylinder head and the cylinder block.
The aluminum gasket superior in heat conduction is also well known other than the metallic gaskets of layered stainless steel sheets, refer to Japanese Patent Publication No. 32746/1982. Moreover, titanium alloy gaskets or titanium-aluminum alloy gaskets of 6Alxe2x80x942Snxe2x80x944Znxe2x80x946Mo alloy, and so on are disclosed in, for example, Japanese Patent Laid-Open Nos. 52267/1993 and 52268/1993.
In an engine composed of an aluminum alloy cylinder head and a cast-iron cylinder block, as the aluminum alloy and cast iron are different from each other in heat conduction and thermal expansion, the metallic gasket is subject to a thermal stress and a thermal distortion, which become unbalance between on one side facing the cylinder head and on the other side facing the cylinder block. With an engine both cylinder head and block are equally made of aluminum alloy, the transfer of hear by conduction is high in the cylinder block so that large difference in temperature is caused between the cylinder head still high in temperature and the cylinder block cooling down rapidly. Nevertheless, the metallic gasket low in heat conductivity has a tendency of offering great resistance or obstruction to the transfer of heat by conduction between the cylinder head and the cylinder block. This creates a major problem in which the internal stress in the cylinder head and the cylinder block is rendered much greater due to beads formed on the stainless steel-made gasket, which is thus much subject to thermal stress and thermal distortion, yielding the inferiority in sealing performance. In addition, the heat radiation from the upper portion of the combustion chamber becomes worse, so that the efficiency of combustion is reduced and consequently the engine will fail to realize the desired performance.
To cope with this, it is desired a head gasket installed between the confronting surfaces of the cylinder head and the cylinder block, which is improved in heat conduction, reduced in a vicious circle of thermal stress and thermal distortion, made simple in construction and further reduced in weight and production cost. In addition, a metallic gasket is needed in which heat is transmitted well from one of the cylinder head and block to another through the gasket, whereby the gasket is improved in durability and reliability.
A primary object of the present invention is to overcome the major problem stated earlier and in particular provide a metallic gasket adapted to be placed between the confronting surfaces of a cylinder head and a cylinder block, which is improved in the transfer of heat by conduction through the gasket to reduce a vicious circle of thermal stress and thermal distortion, made light in weight and inexpensive in production cost. In addition, the head-gasket installation of the present invention helps ensure a good heat transmission between the cylinder head and the cylinder block, improving durability and reliability on sealing effect at the joint between the confronting surfaces, thereby raising the combustion efficiency of the engine.
The present invention is concerned with a metallic gasket adapted disposed between confronting surfaces of engine components with combustion bores to seal a joint between the confronting surfaces when clamping together the engine components opposed to each other, the improvement comprised of a annular raised portion defining inside a gas hole in alignment with any combustion hole in the engine components, a surrounding metallic sheet arranged about the annular raised portion and connected to the annular raised portion, both the annular raised portion and the surrounding metallic sheet being made of aluminum material, and a soft sealing member deposited on the surrounding metallic sheet around the annular raised portion, wherein the annular raised portion and the soft sealing member come in abutment with any mating surface of the confronting surfaces when the gasket is squeezed in place between the confronting surfaces of the components, thereby sealing together the confronting surfaces.
In accordance with one aspect of the present invention, there is provided a metallic gasket wherein the annular raised portion is a single ridge extended around the gas hole and raised thickness-wise of the gasket above a plane of at least any one surface of the surrounding metallic sheet when viewed in an axial section of the gas hole. Alternatively, the annular raised portion includes a radially inside ridge and a radially outside ridge around the gas hole, and both the inside and outside ridges are raised thickness-wise of the gasket above a plane of at least any one surface of the surrounding metallic sheet when viewed in an axial section of the gas hole. As the annular raised portion, whether a single ridge or the combined radially inside and outside ridges, are raised above a plane of at least any one surface of the surrounding metallic sheet, the annular raised portion is compressed between the confronting surfaces when the gasket is squeezed in place between the confronting components, thereby ensuring a row or two rows of high sealing stress.
In accordance with another aspect of the present invention, there is provided a metallic gasket wherein the components are a cylinder block and a cylinder head to be fastened to the cylinder block, the gas hole encircled with the annular raised portion is communicated with associated cylinder bores in the components, and the radially outside ridge of the annular raised portion formed around any one of the adjacent gas holes comes in partially merging with the radially outside ridge of the annular raised portion formed around another of the adjacent gas holes at an area between the adjacent gas holes.
In accordance with another aspect of the present invention, there is provided a metallic gasket wherein the annular raised portion is formed in cross section in any one of circle, ellipse and oval in which a radial inside is made larger thickness-wise of the gasket than a radial outside. Moreover, the annular raised portion is made in any one of solid and hollow constructions. The annular raised portion may be fabricated by any metalworking of forging and pressing processes.
In accordance with a further another aspect of the present invention, there is provided a metallic gasket wherein the annular raised portion is applied with a thermal sprayed coating of aluminum alloy superior in heat resistance and corrosion resistance to improve the gasket in heat resistance, corrosion resistance and strength.
In accordance with another aspect of the present invention, there is provided a metallic gasket wherein the surrounding metallic sheet is of at least an aluminum sheet.
In accordance with another aspect of the present invention, there is provided a metallic gasket wherein the surrounding metallic sheet is of two aluminum sheets while the annular raised portion is composed of a ring body and a lug extending around the ring body, the lug being disposed between the two aluminum sheets.
In a further another aspect of the present invention, there is provided a metallic gasket wherein the surrounding metallic sheet is recessed below any one surface thereof, where the soft sealing member is charged. Moreover, the recess formed along the annular raised portion around any one of the adjacent gas holes comes in merging with the recess formed along the annular raised portion around another of the adjacent gas holes at an area between the adjacent gas holes. The soft sealing member, since adhered and charged in the recess formed in the surface of the surrounding metallic sheet, is securely held on the surrounding metallic sheet.
With the metallic gasket constructed as recited earlier, both the annular raised portion and the soft sealing member, when squeezed between the mating surfaces to fasten together the confronting components, come in engagement with the mating surfaces to help ensure the high sealing performance around the associated gas hole.
Since the metallic gasket of the present invention is made of any aluminum material of commercial-purity aluminum or aluminum alloys, the metallic gasket serves well in heat conduction when installed between, for example the cylinder block and the cylinder head, compared with the gasket of stainless steel sheet, so that there is no obstruction to the transfer of heat by conduction arising the temperature difference between the cylinder block and the cylinder head, and thus the gasket is less subject to thermal deformation and thermal stress, which might otherwise occur in the gasket in itself. This contributes to improvement in strength, heat resistance, durability and reliability of the gasket. Further, the metallic gasket of the present invention does not spoil the heat conduction between the components even if the engine components are made of the substantially same aluminum material as the metallic gasket, and the components are also different in cooling ability.
In the metallic gasket of the present invention, the annular raised portion or ring body around the gas hole is made of aluminum material, and for the sake of which the annular raised portion or ring body, when squeezed, can follow well the deformation in the cylinder block and the cylinder head to be deformed easily depending on the design conditions. This would make realization of uniform sealing stress around the gas hole much easier, with no need of previously varying the thickness or height of the annular raised portion or the ring body circumferentially of the gas hole to ensure the sealing stress uniform around the gas hole. Moreover, the metallic gasket of the present invention is provided with an elastic sealing member extending around the gas hole to help ensure the overall good sealing efficiency. Besides, it will be understood that even when the metallic gasket of the present invention is adopted for the gasket in which the bead is varied previously in height circumferentially of the gas hole to realize the even sealing stress around the gas hole, the sealing stress would be adjusted much more evenly around the gas hole with high accuracy.
The metallic gasket of the present invention is simple in construction, light in weight and also reduced in production cost. Because the aluminum material is low in specific gravity compared with the stainless steel material, it will be sure that the aluminum gasket is made reduced in weight and further the aluminum gasket won""t rise in production cost above the layered construction of stainless steel sheets.
The metallic gasket of the present invention, as comparable in thermal deformation and thermal stress with both the cylinder block and the cylinder head, is less subject to the difference in thermal influence, thereby made uniformed in thermal influence that might otherwise affect the metallic gasket. Further, the metallic gasket of the present invention may serve well keeping the transfer of heat by conduction through the gasket between the cylinder block and the cylinder head, whether the cylinder block and the cylinder head are made of different materials or they are of the same material and also different in cooling ability. Thus, the metallic gasket of the present invention ensures good sealing performance and improvement in durability and reliability.
In addition, the metallic gasket of the present invention helps ensure an even heat distribution in the overall engine, reducing the thermal affection of thermal deformation, thermal stress, and so on, thereby raising the combustion efficiency of the engine.
Other aspects and features of the present invention will be more apparent to those skilled in the art on consideration of the accompanying drawings and following specification wherein are disclosed preferred embodiments of the invention with the understanding that such variations, modifications and elimination of parts may be made therein as fall within the scope of the appended claims without departing from the spirit of the invention.